Lighter Weight Signal-Based Custom Modules

include/modules/custom.hpp

@@ -22,6 +22,7 @@ class Custom : public ALabel {
  private:
   void delayWorker();
   void continuousWorker();
+  void waitingWorker();
   void parseOutputRaw();
   void parseOutputJson();
   void handleEvent();

include/util/sleeper_thread.hpp

@@ -58,6 +58,12 @@ class SleeperThread {
 
   bool isRunning() const { return do_run_; }
 
+  auto sleep() {
+    std::unique_lock lk(mutex_);
+    CancellationGuard cancel_lock;
+    return condvar_.wait(lk);
+  }
+
   auto sleep_for(std::chrono::system_clock::duration dur) {
     std::unique_lock lk(mutex_);
     CancellationGuard cancel_lock;

man/waybar-custom.5.scd

@@ -34,7 +34,8 @@ Addressed by *custom/<name>*
 	typeof: integer ++
 	The interval (in seconds) in which the information gets polled. ++
 	Use *once* if you want to execute the module only on startup. ++
-	You can update it manually with a signal. If no *interval* is defined, it is assumed that the out script loops it self.
+	You can update it manually with a signal. If no *interval* or *signal* is defined, it is assumed that the out script loops it self. ++
+	If a *signal* is defined then the script will run once on startup and will will only update with a signal.
 
 *restart-interval*: ++
 	typeof: integer ++
@@ -45,7 +46,8 @@ Addressed by *custom/<name>*
 *signal*: ++
 	typeof: integer ++
 	The signal number used to update the module. ++
-	The number is valid between 1 and N, where *SIGRTMIN+N* = *SIGRTMAX*.
+	The number is valid between 1 and N, where *SIGRTMIN+N* = *SIGRTMAX*. ++
+	If no interval is defined then a signal will be the only way to update the module.
 
 *format*: ++
 	typeof: string ++

src/modules/custom.cpp

@@ -11,11 +11,13 @@ waybar::modules::Custom::Custom(const std::string& name, const std::string& id,
       fp_(nullptr),
       pid_(-1) {
   dp.emit();
-  if (interval_.count() > 0) {
+  if (!config_["signal"].empty() && config_["interval"].empty()) {
+    waitingWorker();
+  } else if (interval_.count() > 0) {
     delayWorker();
   } else if (config_["exec"].isString()) {
     continuousWorker();
-  }
+  } 
 }
 
 waybar::modules::Custom::~Custom() {
@@ -92,6 +94,26 @@ void waybar::modules::Custom::continuousWorker() {
   };
 }
 
+void waybar::modules::Custom::waitingWorker() {
+  thread_ = [this] {
+    bool can_update = true;
+    if (config_["exec-if"].isString()) {
+      output_ = util::command::execNoRead(config_["exec-if"].asString());
+      if (output_.exit_code != 0) {
+        can_update = false;
+        dp.emit();
+      }
+    }
+    if (can_update) {
+      if (config_["exec"].isString()) {
+        output_ = util::command::exec(config_["exec"].asString());
+      }
+      dp.emit();
+    }
+    thread_.sleep();
+  };
+}
+
 void waybar::modules::Custom::refresh(int sig) {
   if (sig == SIGRTMIN + config_["signal"].asInt()) {
     thread_.wake_up();